scholarly journals The ultraviolet colour component enhances the attractiveness of red flowers of a bee-pollinated plant

2020 ◽  
Vol 13 (3) ◽  
pp. 354-360 ◽  
Author(s):  
Zhe Chen ◽  
Chang-Qiu Liu ◽  
Hang Sun ◽  
Yang Niu
Keyword(s):  
Limited Attention ◽  
Spectral Purity ◽  
Chromatic Contrast ◽  
Colour Perception ◽  
Lab Experiments ◽  
Achromatic Contrast ◽  
Phenotypic Manipulation ◽  
Colour Preferences ◽  
Uv Reflection

Abstract Aims Bee-pollinated flowers are rarely red, presumably because bees (which lack red receptors) have difficulty detecting red targets. Although the response of bees to red colour has been investigated in lab experiments, most stimuli have been pure red, while the subtle diversity of red as perceived by humans (human-red) has received very limited attention. Here we test the hypothesis that ultraviolet (UV) reflected from human-red flowers enhances their attractiveness to bees, through increased chromatic contrast. Methods Using Onosma confertum (Boraginaceae), a plant with UV-reflecting red flowers that are pollinated by bumblebees, we investigated the effects of UV reflection on pollinator responses by conducting phenotypic manipulation experiments in the field. Colour preferences of flower-naïve bumblebees were also examined. Colour perception by bumblebees was estimated in terms of chromatic and achromatic contrast, based on two different colour perception models. Important Findings We found that both natural and flower-naïve bumblebees strongly preferred visiting UV-reflecting targets compared with UV-absorbing ones. Colour models show that the UV-reflecting flowers exhibit higher spectral purity and higher chromatic contrast against the foliage background, whereas they have similar achromatic contrast in terms of green receptor contrast. These results indicate that the component of UV reflection increases chromatic contrast in O. confertum, enhancing the visual attractiveness of these red flowers to bumblebees. We further infer that the secondary reflectance might be a necessary component in human-red flowers that are primarily pollinated by animals without red receptors, such as bees.

scholarly journals Red flowers differ in shades between pollination systems and across continents

2020 ◽  
Vol 126 (5) ◽  
pp. 837-848 ◽  
Author(s):  
Zhe Chen ◽  
Yang Niu ◽  
Chang-Qiu Liu ◽  
Hang Sun
Keyword(s):  
Large Scale ◽  
New World ◽  
Floral Colour ◽  
Chromatic Contrast ◽  
Colour Perception ◽  
Old World ◽  
Primary Signal ◽  
Achromatic Contrast ◽  
Pollination Systems ◽  
Plant Pollinator

Abstract Background and Aims Floral colour is a primary signal in plant–pollinator interactions. The association between red flowers and bird pollination is well known, explained by the ‘bee avoidance’ and ‘bird attraction’ hypotheses. Nevertheless, the relative importance of these two hypotheses has rarely been investigated on a large scale, even in terms of colour perception per se. Methods We collected reflectance spectra for 130 red flower species from different continents and ascertained their pollination systems. The spectra were analysed using colour vision models for bees and (three types of) birds, to estimate colour perception by these pollinators. The differences in colour conspicuousness (chromatic and achromatic contrast, purity) and in spectral properties between pollination systems and across continents were analysed. Key Results Compared with other floral colours, red flowers are very conspicuous to birds and much less conspicuous to bees. The red flowers pollinated by bees and by birds are more conspicuous to their respective pollinators. Compared with the bird flowers in the Old World, the New World ones are less conspicuous to bees and may be more conspicuous not only to violet-sensitive but also to ultraviolet-sensitive birds. These differences can be explained by the different properties of the secondary reflectance peak (SP). SP intensity is higher in red flowers pollinated by bees than those pollinated by birds (especially New World bird flowers). A transition from high SP to low SP in red flowers can induce chromatic contrast changes, with a greater effect on reducing attraction to bees than enhancing attraction to birds. Conclusions Shades of red flowers differ between pollination systems. Moreover, red bird flowers are more specialized in the New World than in the Old World. The evolution towards colour specialization is more likely to result in higher efficiency of bee avoidance than bird attraction

Attentional capture helps explain why moral and emotional content go viral

2019 ◽  
Author(s):  
William J. Brady ◽  
Ana P. Gantman ◽  
Jay Joseph Van Bavel
Keyword(s):  
Social Media ◽  
Attentional Capture ◽  
Emotional Content ◽  
Limited Attention ◽  
Psychological Process ◽  
Emotional Stimuli ◽  
Political Leaders ◽  
Lab Experiments ◽  
Perceptual Systems ◽  
Shed Light

Our social media newsfeeds are filled with a variety of content all battling for our limited attention. Across three studies, we investigated whether moral and emotional content captures our attention more than other content and if this may help explain why this content is more likely to go viral online. Using a combination of controlled lab experiments and nearly 50,000 political tweets, we found that moral and emotional content are prioritized in early visual attention more than neutral content, and that such attentional capture is associated with increased retweets during political conversations online. Furthermore, we found that the differences in attentional capture among moral and emotional stimuli could not be fully explained by differences in arousal. These studies suggest that attentional capture is one basic psychological process that helps explain the increased diffusion of moral and emotional content during political discourse on social media, and shed light on ways in which political leaders, disinformation profiteers, marketers, and activist organizations can spread moralized content by capitalizing on natural tendencies of our perceptual systems.

scholarly journals Triggerfish uses chromaticity and lightness for object segregation

2017 ◽  
Vol 4 (12) ◽  
pp. 171440 ◽  
Author(s):  
Laurie Mitchell ◽  
Karen L. Cheney ◽  
Fabio Cortesi ◽  
N. Justin Marshall ◽  
Misha Vorobyev
Keyword(s):  
Visual Perception ◽  
Human Visual Perception ◽  
Chromatic Contrast ◽  
Visual Patterns ◽  
Ishihara Test ◽  
Achromatic Contrast ◽  
Chromatic Cues ◽  
Object Segregation

Humans group components of visual patterns according to their colour, and perceive colours separately from shape. This property of human visual perception is the basis behind the Ishihara test for colour deficiency, where an observer is asked to detect a pattern made up of dots of similar colour with variable lightness against a background of dots made from different colour(s) and lightness. To find out if fish use colour for object segregation in a similar manner to humans, we used stimuli inspired by the Ishihara test. Triggerfish ( Rhinecanthus aculeatus ) were trained to detect a cross constructed from similarly coloured dots against various backgrounds. Fish detected this cross even when it was camouflaged using either achromatic or chromatic noise, but fish relied more on chromatic cues for shape segregation. It remains unknown whether fish may switch to rely primarily on achromatic cues in scenarios where target objects have higher achromatic contrast and lower chromatic contrast. Fish were also able to generalize between stimuli of different colours, suggesting that colour and shape are processed by fish independently.

scholarly journals Australian native flower colours: does nectar reward drive bee pollinator flower preferences?

2019 ◽  
Author(s):  
Mani Shrestha ◽  
Jair E Garcia ◽  
Martin Burd ◽  
Adrian G Dyer
Keyword(s):  
Flower Colour ◽  
Chromatic Contrast ◽  
Nectar Volume ◽  
Eastern Australia ◽  
Significant Difference ◽  
Flower Colours ◽  
Colour Category ◽  
Colour Preferences ◽  
Nectar Rewards ◽  
Colour Signals

AbstractColour is an important signal that flowering plants use to attract insect pollinators like bees. Previous research in Germany has shown that nectar volume is higher for flower colours that are innately preferred by European bees, suggesting an important link between colour signals, bee preferences and floral rewards. In Australia, flower colour signals have evolved in parallel to the Northern hemisphere to enable easy discrimination and detection by the phylogenetically ancient trichromatic visual system of bees, and native Australian bees also possess similar innate colour preferences to European bees. We measured 59 spectral signatures from flowers present at two preserved native habitats in South Eastern Australia and tested whether there were any significant differences in the frequency of flowers presenting higher nectar rewards depending upon the colour category of the flower signals, as perceived by bees. We also tested if there was a significant correlation between chromatic contrast and the frequency of flowers presenting higher nectar rewards. For the entire sample, and for subsets excluding species in the Asteraceae and Orchidaceae, we found no significant difference among colour categories in the frequency of high nectar reward. This suggests that whilst such relationships between flower colour signals and nectar volume rewards have been observed at a field site in Germany, the effect is likely to be specific at a community level rather than a broad general principle that has resulted in the common signalling of bee flower colours around the world.

scholarly journals Spatio-chromatic contrast sensitivity across the lifespan: interactions between age and light level in high dynamic range

2020 ◽  
Vol 2020 (28) ◽  
pp. 65-69
Author(s):  
Maliha Ashraf ◽  
Sophie Wuerger ◽  
Minjung Kim ◽  
Jasna Martinovic ◽  
Rafał K. Mantiuk
Keyword(s):  
Contrast Sensitivity ◽  
Dynamic Range ◽  
High Dynamic Range ◽  
Light Level ◽  
Background Luminance ◽  
Age Group ◽  
Chromatic Contrast ◽  
Achromatic Contrast ◽  
High Dynamic ◽  
Chromatic Contrast Sensitivity

We investigated spatio-chromatic contrast sensitivity in both younger and older color-normal observers. We tested how the adapting light level affected the contrast sensitivity and whether there was a differential age-related change in sensitivity. Contrast sensitivity was measured along three directions in colour space (achromatic, red-green, yellowish-violet), at background luminance levels from 0.02 to 2000 cd/m2, and different stimuli sizes using 4AFC method on a high dynamic range display. 20 observers with a mean age of 33 y. o. a. and 20 older observers with mean age of 65 participated in the study. Within each session, observers were fully adapted to the fixed background luminance. Our main findings are: (1) Contrast sensitivity increases with background luminance up to around 200 cd/m2, then either declines in case of achromatic contrast sensitivity, or remains constant in case of chromatic contrast sensitivity; (2) The sensitivity of the younger age group is higher than that for the older age group by 0.3 log units on average. Only for the achromatic contrast sensitivity, the old age group shows a relatively larger decline in sensitivity for medium to high spatial frequencies at high photopic light levels; (3) Peak frequency, peak sensitivity and cut-off frequency of contrast sensitivity functions show decreasing trends with age and the rate of this decrease is dependent on mean luminance. The data is being modeled to predict contrast sensitivity as a function of age, luminance level, spatial frequency, and stimulus size.

Apparent Relative Motion from a Checkerboard Surround

Perception ◽  
1997 ◽  
Vol 26 (7) ◽  
pp. 831-846 ◽  
Author(s):  
Byung-Geun Khang ◽  
Edward A Essock
Keyword(s):  
Phase Shift ◽  
Relative Motion ◽  
Gain Control ◽  
Chromatic Contrast ◽  
Common Fate ◽  
Spatial Properties ◽  
Test Grating ◽  
Achromatic Contrast ◽  
Constituent Elements ◽  
Possible Cause

To better understand the Ouchi illusion in which a stationary picture generates illusory relative motion, the spatial properties of the constituent elements of the rectangular checkerboard background were examined. Results of experiment 1 revealed that the largest illusion was obtained with elements of approximately 20–30 min in width and 4–6 min in height, an orientation of the constituents that was orthogonal to that of the test grating, and a phase shift of the alternate stripes that was close to 180°. In experiment 2 it was found that the illusion increased in magnitude with increasing achromatic contrast but was minimal with a pattern of high chromatic contrast near isoluminance. In experiment 3, two test patches were presented simultaneously in the checkerboard background and were varied independently in their orientation to explore whether or not their motions were perceived as coherent (common fate). Patches having identical orientations, and nearly orthogonal to the surround, were synchronized more strongly than those having reflected orientations. Hysteresis related to the gain control of spatially overlapping visual units differing in their polarity (ON/OFF) was discussed as a possible cause of this phenomenon.

scholarly journals Assessing bird avoidance of high-contrast lights using a choice test approach: implications for reducing human-induced avian mortality

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5404 ◽  
Author(s):  
Benjamin Goller ◽  
Bradley F. Blackwell ◽  
Travis L. DeVault ◽  
Patrice E. Baumhardt ◽  
Esteban Fernández-Juricic
Keyword(s):  
Light Emitting Diode ◽  
Visual Saliency ◽  
Choice Test ◽  
Visual Perspective ◽  
Chromatic Contrast ◽  
Light Emitting ◽  
Behavioral Assay ◽  
Achromatic Contrast ◽  
Species Specific ◽  
Led Lights

Background Avian collisions with man-made objects and vehicles (e.g., buildings, cars, airplanes, power lines) have increased recently. Lights have been proposed to alert birds and minimize the chances of collisions, but it is challenging to choose lights that are tuned to the avian eye and can also lead to avoidance given the differences between human and avian vision. We propose a choice test to address this problem by first identifying wavelengths of light that would over-stimulate the retina using species-specific perceptual models and by then assessing the avoidance/attraction responses of brown-headed cowbirds to these lights during daytime using a behavioral assay. Methods We used perceptual models to estimate wavelength-specific light emitting diode (LED) lights with high chromatic contrast. The behavioral assay consisted of an arena where the bird moved in a single direction and was forced to make a choice (right/left) using a single-choice design (one side with the light on, the other with the light off) under diurnal light conditions. Results First, we identified lights with high saliency from the cowbird visual perspective: LED lights with peaks at 380 nm (ultraviolet), 470 nm (blue), 525 nm (green), 630 nm (red), and broad-spectrum (white) LED lights. Second, we found that cowbirds significantly avoided LED lights with peaks at 470 and 630 nm, but did not avoid or prefer LED lights with peaks at 380 and 525 nm or white lights. Discussion The two lights avoided had the highest chromatic contrast but relatively lower levels of achromatic contrast. Our approach can optimize limited resources to narrow down wavelengths of light with high visual saliency for a target species leading to avoidance. These lights can be used as candidates for visual deterrents to reduce collisions with man-made objects and vehicles.

scholarly journals In a Neotropical Periurban Park, Fruit Consumption by Birds Seems to Be a Random Process

2021 ◽  
Vol 9 ◽  
Author(s):  
Issaac Azrrael Teodosio-Faustino ◽  
Edgar Chávez-González ◽  
Ernesto Ruelas Inzunza
Keyword(s):  
Random Process ◽  
Probabilistic Models ◽  
Null Model ◽  
Interaction Network ◽  
Chromatic Contrast ◽  
Fruit Consumption ◽  
Pairwise Interactions ◽  
Multiple Variable ◽  
Achromatic Contrast

Frugivory interactions between birds and fruit-bearing plants are shaped by the abundance of its interacting species, their temporal overlap, the matching of their morphologies, as well as fruit and seed characteristics. Our study evaluates the role of seven factors of fruits and plants in determining the frequency of whole-fruit consumption by birds. We studied the frugivory network of a Neotropical periurban park in Xalapa, Veracruz, Mexico, and quantified relative abundance and phenology of birds and fruit, as well as fruit morphology, chromatic and achromatic contrast, and nutritional content. Using a maximum likelihood approach, we compared the observed interaction network with 62 single- and multiple-variable probabilistic models. Our network is composed of 11 plants and 17 birds involved in 81 frugivory interactions. This network is nested, modular, and relatively specialized. However, the frequency of pairwise interactions is not explained by the variables examined in our probabilistic models and found the null model has the best performance. This indicates that no single predictor or combination of them is better at explaining the observed frequency of pairwise interactions than the null model. The subsequent four top-ranking models, with ΔAIC values < 100, are single-variable ones: carbohydrate content, lipid content, chromatic contrast, and morphology. Two- and three-variable models show the poorest fit to observed data. The lack of a deterministic pattern does not support any of our predictions nor neutral- or niche-based processes shaping the observed pattern of fruit consumption in our interaction network. It may also mean that fruit consumption by birds in this periurban park is a random process. Although our study failed to find a pattern, our work exemplifies how investigations done in urban settings, poor in species and interactions, can help us understand the role of disturbance in the organization of frugivory networks and the processes governing their structure.

scholarly journals Comparison of Visibility Threshold on Different Chromatic Contrast Objects

2016 ◽  
Vol 13 (1) ◽  
pp. 105
Author(s):  
Saiful Azlan Rosli ◽  
Anis Zahirah Aladin ◽  
Nurulain Muhamad ◽  
Ai Hong Chen
Keyword(s):  
Ocular Diseases ◽  
Chromatic Contrast ◽  
Colour Perception ◽  
Corrected Visual Acuity ◽  
History Of ◽  
Normal Colour ◽  
Blue Background ◽  
Average Visibility ◽  
Best Corrected Visual Acuity ◽  
Landolt C

The aim of this study was to compare the visibility threshold of eight plates with different chromatic contrast. The staircase psychophysics method based on the resolution of gaps in Landolt C was used to determine the average visibility threshold. Thirty young adults with best-corrected visual acuity of 6/6, normal colour perception and no history of ocular diseases were recruited. The results showed a combination of white on blue background plate gave a highest visibility level (mean=44.48±6.37m), while red on a blue background was the least visible combination (mean=33.30±4.68m). In conclusion, the chromatic contrast of an object can affect the visibility threshold. Keywords: chromatic contrast, visibility threshold

scholarly journals Chromatic and achromatic monocular deprivation produce separable changes of eye dominance in adults

2017 ◽  
Vol 284 (1867) ◽  
pp. 20171669 ◽  
Author(s):  
Jiawei Zhou ◽  
Alexandre Reynaud ◽  
Yeon Jin Kim ◽  
Kathy T. Mullen ◽  
Robert F. Hess
Keyword(s):  
Contrast Sensitivity ◽  
Monocular Deprivation ◽  
Chromatic Contrast ◽  
Eye Dominance ◽  
Colour Contrast ◽  
Human Adults ◽  
Achromatic Contrast ◽  
Perceptual Changes ◽  
Chromatic Contrast Sensitivity

Temporarily depriving one eye of its input, in whole or in part, results in a transient shift in eye dominance in human adults, with the patched eye becoming stronger and the unpatched eye weaker. However, little is known about the role of colour contrast in these behavioural changes. Here, we first show that the changes in eye dominance and contrast sensitivity induced by monocular eye patching affect colour and achromatic contrast sensitivity equally. We next use dichoptic movies, customized and filtered to stimulate the two eyes differentially. We show that a strong imbalance in achromatic contrast between the eyes, with no colour content, also produces similar, unselective shifts in eye dominance for both colour and achromatic contrast sensitivity. Interestingly, if this achromatic imbalance is paired with similar colour contrast in both eyes, the shift in eye dominance is selective, affecting achromatic but not chromatic contrast sensitivity and revealing a dissociation in eye dominance for colour and achromatic image content. On the other hand, a strong imbalance in chromatic contrast between the eyes, with no achromatic content, produces small, unselective changes in eye dominance, but if paired with similar achromatic contrast in both eyes, no changes occur. We conclude that perceptual changes in eye dominance are strongly driven by interocular imbalances in achromatic contrast, with colour contrast having a significant counter balancing effect. In the short term, eyes can have different dominances for achromatic and chromatic contrast, suggesting separate pathways at the site of these neuroplastic changes.

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